The invention relates to an internal combustion engine having a variable compression ratio obtained by varying the length of the connecting rods of the piston, the position of the crankshaft or the position of the cylinder head relative to the cylinder.
EP 1 307 642 B1 discloses a reciprocating-piston internal combustion engine having a device for varying the compression ratio. The device has, in particular for one cylinder of the internal combustion engine, a main connecting rod which is connected to a piston, a transverse lever which is connected by means of pivot joints to the main connecting rod and to the crankshaft, an auxiliary connecting rod which is connected by means of pivot joints to a transverse lever and to an eccentric which is assigned to the at least one cylinder, and a drive device for an adjusting shaft on which the eccentric is arranged.
By means of rotation of the adjusting shaft and therefore by means of rotation of the eccentric, the position and the setting of the auxiliary piston rod and of the trans-verse lever are adjustable. The position of the piston of the internal combustion engine is therefore moved, and the compression ratio is therefore varied. The adjusting shaft with the eccentric performs a rotational movement which is synchronous with the crankshaft, or it is rotated by means of an adjusting mechanism (not shown specifically). This known device is suitable for adjusting the compression ratio while simultaneously improving the engine operating smoothness.
DE 30 04 402 A1 shows a device for adjusting the compression ratio of reciprocating-piston internal combustion engines, in which the center of the crankshaft can be adjusted relative to the position of the cylinders via an eccentric bearing arrangement, as a result of which the compression ratio is changed.
EP 0 640 176 B1 likewise discloses a device for adjusting the compression ratio of reciprocating-piston internal combustion engines, in which the cylinders are tilted relative to the housing of the internal combustion engine via an eccentric, which is mounted on an adjusting shaft, and levers. In this way, the position of the upper edge of the cylinders changes relative to the center of the crankshaft, and, as a result, a variation of the compression ratio takes place during the adjusting process.
DE 102 21 334 A1 likewise describes a device for adjusting the compression ratio of reciprocating-piston internal combustion engines, in which, similarly to EP 0 640 176 B1, the upper edge of the cylinders is moved relative to the center of the crankshaft. In this case, the upper part of the cylinder housing is moved in a translatory fashion by means of two eccentrics which are mounted on adjusting shafts, and the compression ratio is thereby varied.
DE 100 26 634 A1 likewise discloses a device for adjusting the compression ratio of reciprocating-piston internal combustion engines, in which an eccentric is arranged between the piston rod and the piston of the internal combustion engine. Said eccentric can be adjusted externally by an adjusting shaft via levers, as a result of which the compression ratio is likewise changed.
A feature of all of the above-mentioned reciprocating-piston internal combustion engines is the variation of the compression ratio by means of rotation of at least one adjusting shaft.
It is an object of the present invention to provide a mechanism for facilitating rotation of an adjusting shaft for changing the transmission ratio of an engine by a simple and compact means and with little energy input.